(1968-77 NSU Ro-80). NSU was a German brand that, like many others, began with motorcycle production in the late 1890s. In the 1960s, NSU pioneered development of the Wankel rotary engine which eschewed traditional pistons. NSU merged with Auto Union in 1969, and this model was sold in the U.S. as late as 1977. A twin-rotor engine of 129 horsepower drove the front wheels. (Photo credit: Sean Connor)